1.Installing TYPO3 CMS Screenshot
2.Ubuntu & PHP Version
3.PHP.ini Config
4.TYPO3 Version
In many cases, activating extension=intl in your php.ini and restarting Apache will solve the problem.
In my case, using Windows, this was not sufficient: Additionally, I had to add the php install directory to my windows path variable!
Details about this can be found here: intl extension: installing php_intl.dll